Backlash can occur in low-reduction-ratio gear drives that are available at present, none of which are free of backlash like wave gear drives are. Backlash-free wave gear drives typically have high reduction ratios; i.e., 1/50 or higher The operating principle dictates that these wave gear drives are not suitable for use as low-reduction-ratio gear drives that have a reduction ratio of approximately 1/10. Cup, silk-hat, and flat wave gear devices are disclosed in Patent Documents 1, 2.    [Patent Document 1] Japanese Patent No. 3942249    [Patent Document 2] Japanese Patent No. 2796109